This invention relates to electrosurgical instruments, and more particularly to electrosurgical instruments coated with stick resistant electroconductive amorphous silica coating.
In carrying out electrosurgical procedures, an electrosurgical instrument is used which can be energized by a radio frequency voltage source for cutting tissue and/or coagulating blood through cauterization. Such instruments commonly incorporate a conductive blade in either a "monopolar" or "bipolar" system. Although these electrosurgical instruments have proved effective for controlling bleeding during surgery, a common problem associated with the instruments is "tissue-sticking" to the cutting surface and consequently a reduction in cutting efficiency that requires early replacement of the cutting element. One approach to this problem has been to coat the cutting element with some type of non-stick material to which cauterized tissue is less likely to adhere. Of course, such coating material must be suitable for passing electrosurgical current or at least the coating of the material must be arranged to allow passage of current from the cutting surface to the tissue. Illustrative of prior art patents disclosing anti-stick coatings on electrosurgical instruments are U.S. Pat. Nos. 3,754,329, 4,012,551, 4,314,559, 4,222,467, 4,161,950 and 4,481,057.
Although coating electrosurgical instruments with non-stick materials has improved the efficiency of surgical procedures, the coating materials of the prior art still have their shortcomings. For instance, all have been criticized for presenting one or more of the following problems: (1) less than satisfactory electrical conductivity, (2) poor adhesion to the substrate, (3) a tendency to degrade and abrade under the hemostatic and cauterizing currents used during surgery, (4) poor radiation heat transfer reflectivity properties and "outgassing" due to the low melting temperature of the coating material, and (5) reusable surgical instruments undergo surface corrosion and pitting as a result of repeated sterilization cycles. All of these problems result in the cutting surfaces of the electrosurgical instruments becoming coated with charred tissue.